- New lib/cascade.ts: detect when PATCH extends endTime beyond original,
query same-groomer downstream active appointments, and shift them
forward by (overrunEnd + buffer − downstreamStart). Propagates
through the chain until no more conflicts.
- Cascade result (shifted[], flaggedForReview[], cascadeLog[]) included
in the PATCH response when a shift occurs. Clients receive reschedule
email notification. Out-of-business-hours shifts are flagged rather
than auto-applied.
- Added cascadeDelay() and cascadeOnStatusOverrun() helpers.
- Cascade wired into the this_only PATCH path in appointments.ts.
Tests: cascade.test.ts
UAT: apps/api/UAT_PLAYBOOK.md §2
Refs: GRO-1175, GRO-1162-G
Co-Authored-By: Paperclip <noreply@paperclip.ing>
